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Alveolar development and repair require tight spatiotemporal regulation of numerous signalling pathways that are influenced by chemical and mechanical stimuli. Mesenchymal cells play key roles in numerous developmental processes. Transforming growth factor-β (TGFβ) is essential for alveologenesis and lung repair, and the G protein α subunits Gαq and Gα11 (Gαq/11) transmit mechanical and chemical signals to activate TGFβ in epithelial cells. To understand the role of mesenchymal Gαq/11 in lung development, we generated constitutive (Pdgfrb-Cre+/-;Gnaqfl/fl;Gna11-/-) and inducible (Pdgfrb-Cre/ERT2+/-;Gnaqfl/fl;Gna11-/-) mesenchymal Gαq/11 deleted mice. Mice with constitutive Gαq/11 gene deletion exhibited abnormal alveolar development, with suppressed myofibroblast differentiation, altered mesenchymal cell synthetic function, and reduced lung TGFβ2 deposition, as well as kidney abnormalities. Tamoxifen-induced mesenchymal Gαq/11 gene deletion in adult mice resulted in emphysema associated with reduced TGFβ2 and elastin deposition. Cyclical mechanical stretch-induced TGFβ activation required Gαq/11 signalling and serine protease activity, but was independent of integrins, suggesting an isoform-specific role for TGFβ2 in this model. These data highlight a previously undescribed mechanism of cyclical stretch-induced Gαq/11-dependent TGFβ2 signalling in mesenchymal cells, which is imperative for normal alveologenesis and maintenance of lung homeostasis. [ABSTRACT FROM AUTHOR]

Peptic ulcer disease is a frequent clinical problem with potentially serious complications such as bleeding or perforation. A decisive factor in the pathogenesis of peptic ulcers is gastric acid, the secretion of which is controlled by the hormone gastrin released from gastric G cells. However, the molecular mechanisms regulating gastrin plasma concentrations are poorly understood. Here, we identified a semaphorin-plexin signaling pathway that operates in gastric G cells to inhibit gastrin expression on a transcriptional level, thereby limiting food-stimulated gastrin release and gastric acid secretion. Using a systematic siRNA screening approach combined with biochemical, cell biology, and in vivo mouse experiments, we found that the RasGAP protein Rasal1 is a central mediator of plexin signal transduction, which suppresses gastrin expression through inactivation of the small GTPase R-Ras. Moreover, we show that Rasal1 is pathophysiologically relevant for the pathogenesis of peptic ulcers induced by nonsteroidal anti-inflammatory drugs (NSAIDs), a main risk factor of peptic ulcers in humans. Last, we show that application of recombinant semaphorin 4D alleviates peptic ulcer disease in mice in vivo, demonstrating that this signaling pathway can be harnessed pharmacologically. This study unravels a mode of G cell regulation that is functionally important in gastric homeostasis and disease. Easing gastric acid: Proton pump inhibitors are commonly used to treat gastric acid–related issues, but these drugs may have serious long-term side effects. Xu et al. show that semaphorin-plexin-RasGAP signaling represses gastrin mRNA expression and food-induced gastric acid secretion. Intravenous administration of semaphorin 4D ameliorated nonsteroidal anti-inflammatory drug–induced peptic ulcers in mouse models. This paper establishes a signaling axis that may help in the treatment of peptic ulcer disease. [ABSTRACT FROM AUTHOR]

5 is: Graph This replaces the previously incorrect version: Graph This has been corrected in both the HTML and PDF versions of the article. 5b, in which the image showing stromal vascular fraction (SVF) exposed to conditioned medium of adipocytes from knock-out mice fed standard diet (KO-SD) is also presented to illustrate the condition in which SVF was exposed to conditioned medium of adipocytes from wild-type mice fed standard diet (WT-SD). [Extracted from the article]

G-protein coupled receptors (GPCRs), which activate heterotrimeric G proteins, are an essential class of transmembrane receptors that are responsible for a myriad of signaling events in normal and pathologic conditions. Two members of the G protein family, Gαq and Gα11, activate one of the main GPCR pathways and function as oncogenes by integrating mitogen-stimulated signaling cascades that are active under malignant conditions. Recently, it has been shown that targeted deletion of Gα11 and Gαq from endothelial cells impairs the Rho-mediated formation of focal adherens junctions, suggesting that Gα11/q signaling may also play a significant role in cytoskeletal-mediated cellular responses in epithelial cells. Indeed, combined deletion of Gα11 and Gαq confers a significant migratory defect in keratinocytes that delays cutaneous wound healing in an in vivo setting. This delay can be attributed to a defect during the reepithelialization phase due to significantly attenuated migratory capacity of Gαq-null keratinocytes under combined Gα11 deficiency. In fact, cells lacking Gα11/q demonstrate a severely reduced ability to respond to mitogenic and migratory signals in the microenvironment, leading to inappropriate and premature terminal differentiation. These results suggest that Gα11/q signaling pathways may be critical for integrating mitogenic signals and cytoskeletal function to achieve normal physiological responses. Emergence of a malignant phenotype may therefore arise from both under- and overexpression of Gα11/q signaling, implicating its upstream regulation as a potential therapeutic target in a host of pathologic conditions. [ABSTRACT FROM AUTHOR]

Diabetes strongly associates with microvascular complications that ultimately promote multiorgan failure. Altered myogenic responsiveness compromises tissue perfusion, aggravates hypertension, and sets the stage for later permanent structural changes to the microcirculation. We demonstrate that skeletal muscle resistance arteries isolated from patients with diabetes have augmented myogenic tone, despite reasonable blood glucose control. To understand the mechanisms, we titrated a standard diabetes mouse model (high-fat diet plus streptozotocin [HFD/STZ]) to induce a mild increase in blood glucose levels. HFD/STZ treatment induced a progressive myogenic tone augmentation in mesenteric and olfactory cerebral arteries; neither HFD nor STZ alone had an effect on blood glucose or resistance artery myogenic tone. Using gene deletion models that eliminate tumor necrosis factor (TNF) or sphingosine kinase 1, we demonstrate that vascular smooth muscle cell TNF drives the elevation of myogenic tone via enhanced sphingosine-1-phosphate (S1P) signaling. Therapeutically antagonizing TNF (etanercept) or S1P (JTE013) signaling corrects this defect. Our investigation concludes that vascular smooth muscle cell TNF augments resistance artery myogenic vasoconstriction in a diabetes model that induces a small elevation of blood glucose. Our data demonstrate that microvascular reactivity is an early disease marker and advocate establishing therapies that strategically target the microcirculation. [ABSTRACT FROM AUTHOR]

Aims Arterial hypertension is a major risk factor for cardiovascular diseases. The kidney and its natriuretic function are in the centre of the prevailing models to explain the pathogenesis of hypertension; however, the mechanisms underlying blood pressure elevation remain unclear in most patients. Development of hypertension is strongly correlated with age, and this blood pressure increase typically accelerates in the fourth decade of life. The cause of age-dependent blood pressure elevation is poorly understood. This study aims to understand the role of procontractile G-protein-mediated signalling pathways in vascular smooth muscle in age-dependent hypertension.Methods and results Similar to humans at mid-life, we observed in 1-year-old mice elevated blood pressure levels without any evidence for increased vessel stiffness, impaired renal function, or endocrine abnormalities. Hypertensive aged mice showed signs of endothelial dysfunction and had an increased vascular formation of reactive oxygen species (ROS) and elevated endothelial ET-1 expression. Age-dependent hypertension could be normalized by ETA receptor blockade, smooth muscle-specific inactivation of the gene encoding the ETA receptor, as well as by acute disruption of downstream signalling via induction of smooth muscle-specific Gα12/Gα13, Gαq/Gα11, or LARG deficiency using tamoxifen-inducible smooth muscle-specific conditional mouse knock-out models. Induction of smooth muscle-specific ETA receptor deficiency normalized the blood pressure in aged mice despite the continuous presence of signs of endothelial dysfunction.Conclusion Age-dependent blood pressure elevation is due to a highly reversible activation of procontractile signalling in vascular smooth muscle cells indicating that increased vascular tone can be a primary factor in the development of hypertension. [ABSTRACT FROM AUTHOR]

Plexins are widely expressed transmembrane proteins that mediate the cellular effects of semaphorins. The molecular mechanisms of plexin-mediated signal transduction are still poorly understood. Here we show that signalling via B-family plexins leading to the activation of the small GTPase RhoA requires activation of the IκB kinase (IKK)-complex. In contrast, plexin-B-dependent regulation of R-Ras activity is not affected by IKK activity. This regulation of plexin signalling depends on the kinase activity of the IKK-complex, but is independent of NF-κB activation. We confirm that the IKK-complex is active in tumour cells and osteoblasts, and we demonstrate that plexin-B-dependent tumour cell invasiveness and regulation of osteoblast differentiation require an active IKK-complex. This study identifies a novel, NF-κB-independent function of the IKK-complex and shows that IKK directs plexin-B signalling to the activation of RhoA. [ABSTRACT FROM AUTHOR]

The vertebrate central nervous system develops from an epithelium where cells are polarized along the apicobasal axis. Loss of this polarity results in abnormal organ architecture, morphology and proliferation. We found that mutations of the guanine nucleotide exchange factor ArhGEF18 affect apicobasal polarity of the retinal neuroepithelium in medaka fish. We show that ArhGEF18-mediated activation of the small GTPase RhoA is required to maintain apicobasal polarity at the onset of retinal differentiation and to control the ratio of neurogenic to proliferative cell divisions. RhoA signals through Rock2 to regulate apicobasal polarity, tight junction localization and the cortical actin cytoskeleton. The human ArhGEF18 homologue can rescue the mutant phenotype, suggesting a conserved function in vertebrate neuroepithelia. Our analysis identifies ArhGEF18 as a key regulator of tissue architecture and function, controlling apicobasal polarity and proliferation through RhoA activation. We thus identify the control of neuroepithelial apicobasal polarity as a novel role for RhoA signaling in vertebrate development. [ABSTRACT FROM AUTHOR]

Pathological cardiac hypertrophy involves auto/paracrine mediators acting through Gq/11-coupled receptors. A novel signaling route stimulated by βγ-subunits of Gq/11 results in the autophosphorylation of ERK1/2 on a new site and the nuclear retention of ERK1/2, thereby activating hypertrophic gene programs. [Copyright &y& Elsevier]

Transforming growth factor-β (TGF-β) signaling has been significantly implicated in the pathogenesis of aneurysm, prominently the initiation and progression of abdominal aortic aneurysm (AAA). Vascular smooth muscle cell (SMC) is the principal resident cell in aortic wall and is essential for its structure and function. However, the role of TGF-β pathway in SMC for the formation of AAA remains unknown. Therefore, the goal of the present study was to investigate the effect of TGF-β pathway in SMC for AAA pathogenesis, by using a genetical smooth muscle-specific (SM-specific) TGF-βtype II receptor (Tgfbr2) disruption animal model. Mice deficient in the expression of Tgfbr2 (MyhCre.Tgfbr2 f/f and MyhCre.Tgfbr2 WT/f ) and their corresponding wild-type background mice (MyhCre.Tgfbr2 WT/WT ) underwent AAA induction by infrarenal peri-adventitial application of elastase. Fourteen days after elastase treatment, the aortas were analyzed and indicated that disruption of 1 or 2 alleles of Tgfbr2 in SMC provided markedly step-wise protection from AAA formation. And elastin degradation, medial SMC loss, macrophage infiltration, and matrix metalloproteinases (MMP) expression were all significantly reduced in Tgfbr2 deletion mice. Our study demonstrated, for the first time, that the TGF-β signaling pathway in SMC plays a critical role in AAA and disruption can prevent the aneurysm formation. [ABSTRACT FROM AUTHOR]

Although the ability of G protein-coupled receptors to stimulate normal and aberrant cell growth has been intensely investigated, the precise nature of the molecular mechanisms underlying their transforming potential are still not fully understood. In this study, we have taken advantage of the potent mitogenic effect of thrombin and the focus-forming activity of one of its receptors, protease-activated receptor-1, to dissect how this receptor coupled to Gα[sub i], Gα[sub q/11], and Gα[sub 12/13] transduces signals from the membrane to the nucleus to initiate transcriptional events involved in cell transformation. Using endogenous and transfected thrombin receptors in NIH 3T3 cells, ectopic expression of muscarinic receptors coupled to Gα[sub q] and Gα[sub i], and chimeric G protein α subunits and murine fibroblasts deficient in Gα[sub q/11], and Gα[sub 12/13], we show here that, although coupling to Gα[sub i] is sufficient to induce ERK activation, the ability to couple to Gα[sub q] and/or Gα[sub 13] is necessary to induce c-jun expression and cell transformation. Furthermore, we show that Gα[sub q] and Gα[sub 13] can initiate the activation of MAPK cascades, including JNK, p38, and ERK5, which in turn regulate the activity of transcription factors controlling expression from the c-jun promoter. We also present evidence that c-Jun and the kinases regulating its expression are integral components of the transforming pathway initiated by protease-activated receptor-1. [ABSTRACT FROM AUTHOR]

Background: G protein-coupled receptors are important regulators of contractility and differentiation in vascular smooth muscle cells (SMCs), but the specific function of SMC-expressed orphan G protein-coupled receptor class C group 5 member B (GPRC5B) is unclear.Methods: We studied the role of GPRC5B in the regulation of contractility and dedifferentiation in human and murine SMCs in vitro and in iSM-Gprc5b-KO (tamoxifen-inducible, SMC-specific knockout) mice under conditions of arterial hypertension and atherosclerosis in vivo.Results: Mesenteric arteries from SMC-specific Gprc5b-KOs showed ex vivo significantly enhanced prostacyclin receptor (IP)-dependent relaxation, whereas responses to other relaxant or contractile factors were normal. In vitro, knockdown of GPRC5B in human aortic SMCs resulted in increased IP-dependent cAMP production and consecutive facilitation of SMC relaxation. In line with this facilitation of IP-mediated relaxation, iSM-Gprc5b-KO mice were protected from arterial hypertension, and this protective effect was abrogated by IP antagonists. Mechanistically, we show that knockdown of GPRC5B increased the membrane localization of IP both in vitro and in vivo and that GPRC5B, but not other G protein-coupled receptors, physically interacts with IP. Last, we show that enhanced IP signaling in GPRC5B-deficient SMCs not only facilitates relaxation but also prevents dedifferentiation during atherosclerosis development, resulting in reduced plaque load and increased differentiation of SMCs in the fibrous cap.Conclusions: Taken together, our data show that GPRC5B regulates vascular SMC tone and differentiation by negatively regulating IP signaling. [ABSTRACT FROM AUTHOR]

Hypertension is a primary risk factor for cardiovascular diseases including myocardial infarction and stroke. Major determinants of blood pressure are vasodilatory factors such as nitric oxide (NO) released from the endothelium under the influence of fluid shear stress exerted by the flowing blood. Several endothelial signaling processes mediating fluid shear stress-induced formation and release of vasodilatory factors have been described. It is, however, still poorly understood how fluid shear stress induces these endothelial responses. Here we show that the endothelial mechanosensitive cation channel PIEZO1 mediated fluid shear stress-induced release of adrenomedullin, which in turn activated its Gs-coupled receptor. The subsequent increase in cAMP levels promoted the phosphorylation of endothelial NO synthase (eNOS) at serine 633 through protein kinase A (PKA), leading to the activation of the enzyme. This Gs/PKA-mediated pathway synergized with the AKT-mediated pathways leading to eNOS phosphorylation at serine 1177. Mice with endothelium-specific deficiency of adrenomedullin, the adrenomedullin receptor, or Gαs showed reduced flow-induced eNOS activation and vasodilation and developed hypertension. Our data identify fluid shear stress-induced PIEZO1 activation as a central regulator of endothelial adrenomedullin release and establish the adrenomedullin receptor and subsequent Gs-mediated formation of cAMP as a critical endothelial mechanosignaling pathway regulating basal endothelial NO formation, vascular tone, and blood pressure. [ABSTRACT FROM AUTHOR]

Arterial blood pressure is controlled by vasodilatory factors such as nitric oxide (NO) that are released from the endothelium under the influence of fluid shear stress exerted by flowing blood. Flow-induced endothelial release of ATP and subsequent activation of Gq/G11-coupled purinergic P2Y2 receptors have been shown to mediate fluid shear stress-induced stimulation of NO formation. However, the mechanism by which fluid shear stress initiates these processes is unclear. Here, we have shown that the endothelial mechanosensitive cation channel PIEZO1 is required for flow-induced ATP release and subsequent P2Y2/Gq/G11-mediated activation of downstream signaling that results in phosphorylation and activation of AKT and endothelial NOS. We also demonstrated that PIEZO1-dependent ATP release is mediated in part by pannexin channels. The PIEZO1 activator Yoda1 mimicked the effect of fluid shear stress on endothelial cells and induced vasorelaxation in a PIEZO1-dependent manner. Furthermore, mice with induced endothelium-specific PIEZO1 deficiency lost the ability to induce NO formation and vasodilation in response to flow and consequently developed hypertension. Together, our data demonstrate that PIEZO1 is required for the regulation of NO formation, vascular tone, and blood pressure. [ABSTRACT FROM AUTHOR]

Activation of G protein-coupled receptors (GPCRs) can induce vasoconstriction via calcium signal-mediated and Rho-dependent pathways. Earlier reports have shown that diacylglycerol produced during calcium signal generation can be converted to an endocannabinoid, 2-arachidonoylglycerol (2-AG). Our aim was to provide evidence that GPCR signaling-induced 2-AG production and activation of vascular type1 cannabinoid receptors (CB 1 R) is capable of reducing agonist-induced vasoconstriction and hypertension. Rat and mouse aortic rings were examined by myography. Vascular expression of CB 1 R was demonstrated with immunohistochemistry. Rat aortic vascular smooth muscle cells (VSMCs) were cultured for calcium measurements and 2-AG-determination. Inhibition or genetic loss of CB 1 Rs enhanced vasoconstriction induced by angiotensin II (AngII) or phenylephrine (Phe), but not by prostaglandin(PG)F 2α . AngII-induced vasoconstriction was augmented by inhibition of diacylglycerol lipase (tetrahydrolipstatin) and was attenuated by inhibition of monoacylglycerol lipase (JZL184) suggesting a functionally relevant role for endogenously produced 2-AG. In Gα q/11 -deficient mice vasoconstriction was absent to AngII or Phe, which activate G q/11 -coupled receptors, but was maintained in response to PGF 2α . In VSMCs, AngII-stimulated 2-AG-formation was inhibited by tetrahydrolipstatin and potentiated by JZL184. CB 1 R inhibition increased the sustained phase of AngII-induced calcium signal. Pharmacological or genetic loss of CB 1 R function augmented AngII-induced blood pressure rise in mice. These data demonstrate that vasoconstrictor effect of GPCR agonists is attenuated via G q/11 -mediated vascular endocannabinoid formation. Agonist-induced endocannabinoid-mediated CB 1 R activation is a significant physiological modulator of vascular tone. Thus, the selective modulation of GPCR signaling-induced endocannabinoid release has a therapeutic potential in case of increased vascular tone and hypertension. [ABSTRACT FROM AUTHOR]

TGF-β is essential for vascular development; however, excess TGF-β signaling promotes thoracic aortic aneurysm and dissection in multiple disorders, including Marfan syndrome. Since the pathology of TGF-β over-activity manifests primarily within the arterial media, it is widely assumed that suppression of TGF-β signaling in vascular smooth muscle cells will ameliorate aortic disease. We tested this hypothesis by conditional inactivation of Tgfbr2, which encodes the TGF-β type II receptor, in smooth muscle cells of postweanling mice. Surprisingly, the thoracic aorta rapidly thickened, dilated, and dissected in these animals. Tgfbr2 disruption predictably decreased canonical Smad signaling, but unexpectedly increased MAPK signaling. Type II receptor-independent effects of TGF-β and pathological responses by nonrecombined smooth muscle cells were excluded by serologic neutralization. Aortic disease was caused by a perturbed contractile apparatus in medial ceils and growth factor production by adventitial cells, both of which resulted in maladaptive paracrine interactions between the vessel wall compartments. Treatment with rapamycin restored a quiescent smooth muscle phenotype and prevented dissection. Tgfbr2 disruption in smooth muscle cells also accelerated aneurysm growth in a murine model of Marfan syndrome. Our data indicate that basal TGF-β signaling in smooth muscle promotes postnatal aortic wall homeostasis and impedes disease progression. [ABSTRACT FROM AUTHOR]

Abstract: The rich diversity of lipids and the specific signalling pathways they recruit provides tremendous scope for modulation of biological functions. Lysophosphatidylinositol (LPI) is emerging as a key modulator of cell proliferation, migration, and function, and holds important pathophysiological implications due to its high levels in diseased tissues, such as in cancer. Here we report a novel role for LPI in sensitization of peripheral sensory neurons, which was evident as exaggerated sensitivity to painful and innocuous pressure. Histopathological analyses indicated lack of involvement of myelin pathology and immune cell recruitment by LPI. Using pharmacological and conditional genetic tools in mice, we delineated receptor-mediated from non-receptor-mediated effects of LPI and we observed that GPR55, which functions as an LPI receptor when heterologously expressed in mammalian cells, only partially mediates LPI-induced actions in the context of pain sensitization in vivo; we demonstrate that, in vivo, LPI functions by activating Gα13 as well as Gαq/11 arms of G-protein signalling in sensory neurons. This study thus reports a novel pathophysiological function for LPI and elucidates underlying molecular mechanisms. [Copyright &y& Elsevier]

Background--Cardiac remodeling in response to pressure or volume overload plays an important role in the pathogenesis of heart failure. Various mechanisms have been suggested to translate mechanical stress into structural changes, one of them being the release of humoral factors such as angiotensin II and endothelin-1, which in turn promote cardiac hypertrophy and fibrosis. A large body of evidence suggests that the prohypertrophic effects of these factors are mediated by receptors coupled to the GQ/11 family of heterotrimeric G proteins. Most GQ/11 coupled receptors, however, can also activate G proteins of the G12/I3 family, but the role of G12/13 in cardiac remodeling is not understood. Methods and Results--We use siRNA-mediated knockdown in vitro and conditional gene inactivation in vivo to study the role of the G12/13 family in pressure overload-induced cardiac remodeling. We show in detail that inducible cardiomyocyte-specific inactivation of the a subunit of G13, Gɑ13, does not affect basal heart function but protects mice from pressure overload-induced hypertrophy and fibrosis as efficiently as inactivation of Gɑq/11. Furthermore, inactivation of Gɑ13 prevents the development of heart failure up to 1 year after overloading. On the molecular level, we show that Gɑ13, but not Gɑq/n, controls agonist-induced expression of hypertrophy-specific genes through activation of the small GTPase RhoA and consecutive activation of myocardin-related transcription factors. Conclusion--Our data show that the G12/13 family of heterotrimeric G proteins is centrally involved in pressure overload-induced cardiac remodeling and plays a central role in the transition to heart failure. [ABSTRACT FROM AUTHOR]

Diagnosis of metastatic breast cancer is associated with a very poor prognosis. New therapeutic targets are urgently needed, but their development is hampered by a lack of understanding of the mechanisms leading to tumor metastasis. Exemplifying this is the fact that the approximately 30% of all breast cancers overexpressing the receptor tyrosine kinase ErbB-2 are characterized by high metastatic potential and poor prognosis, but the signaling events downstream of ErbB-2 that drive cancer cell invasion and metastasis remain incompletely understood. Here we show that overexpression of ErbB-2 in human breast cancer cell lines leads to phosphorylation and activation of the semaphorin receptor Plexin-B1. This was required for ErbB-2-dependent activation of the pro-metastatic small GTPases RhoA and RhoC and promoted invasive behavior of human breast cancer cells. In a mouse model of ErbB-2-overexpressing breast cancer, ablation of the gene encoding Plexin- B1 strongly reduced the occurrence of metastases. Moreover, in human patients with ErbB-2-overexpressing breast cancer, low levels of Plexin-B1 expression correlated with good prognosis. Our data suggest that Plexin- B1 represents a new candidate therapeutic target for treating patients with ErbB-2-positive breast cancer. [ABSTRACT FROM AUTHOR]

Abstract: Peripheral injury or inflammation leads to a release of mediators capable of binding to a variety of ion channels and receptors. Among these are the 7-transmembrane receptors (G protein-coupled receptors) coupling to Gs, Gi/o, G12/13, or Gq/11 G proteins. Each of the G protein-coupled receptor pathways is involved in nociceptive modulation and pain processing, but the relative contribution of individual signaling pathways in vivo has not yet been worked out. The Gq/G11 signaling branch is of particular interest because it leads to the activation of phospholipase C-β, protein kinase C, the release of calcium from intracellular stores, and it modulates extracellular regulated kinases. To investigate the contribution of the entire Gq/11-signaling pathway in nociceptors towards regulation of pain, we generated double-deficient mice lacking Gq/11 selectively in nociceptors using a conditional gene-targeting approach. We observed that nociceptor-specific loss of Gq and G11 results in reduced pain hypersensitivity following paw inflammation or spared nerve injury. Surprisingly, our behavioral and electrophysiological experiments also indicated defects in basal mechanical sensitivity in Gq/11 mutant mice, suggesting a novel function for Gq/11 in tonic modulation of acute nociception. Patch-clamp recordings revealed changes in voltage-dependent tetrodotoxin-resistant and tetrodotoxin-sensitive sodium channels in nociceptors upon a loss of Gq/11, whereas potassium currents remained unchanged. Our results indicate that the functional role of the Gq/G11 branch of G-protein signaling in nociceptors in vivo not only spans sensitization mechanisms in pathological pain states, but is also operational in tonic modulation of basal nociception and acute pain. [Copyright &y& Elsevier]

A variety of neurotransmitters, gastrointestinal hormones, and metabolic signals are known to potentiate insulin secretion through GPCRs. We show here that beta cell-specific inactivation of the genes encoding the G protein alpha-subunits Galphaq and Galpha11 resulted in impaired glucose tolerance and insulin secretion in mice. Interestingly, the defects observed in Galphaq/Galpha11-deficient beta cells were not restricted to loss of muscarinic or metabolic potentiation of insulin release; the response to glucose per se was also diminished. Electrophysiological recordings revealed that glucose-induced depolarization of isolated beta cells was impaired in the absence of Galphaq/Galpha11, and closure of KATP channels was inhibited. We provide evidence that this reduced excitability was due to a loss of beta cell-autonomous potentiation of insulin secretion through factors cosecreted with insulin. We identified as autocrine mediators involved in this process extracellular nucleotides such as uridine diphosphate acting through the Gq/G11-coupled P2Y6 receptor and extracellular calcium acting through the calcium-sensing receptor. Thus, the Gq/G11-mediated signaling pathway potentiates insulin secretion in response to glucose by integrating systemic as well as autocrine/paracrine mediators. [ABSTRACT FROM AUTHOR]

Plexins are widely expressed transmembrane proteins that, in the nervous system, mediate repulsive signals of semaphorins. However, the molecular nature of plexin-mediated signal transduction remains poorly understood. Here, we demonstrate that plexin-B family members associate through their C termini with the Rho guanine nucleotide exchange factors PDZ-RhoGEF and LARG. Activation of plexin-B1 by semaphorin 4D regulates PDZ-RhoGEF/LARG activity leading to RhoA activation. In addition, a dominant-negative form of PDZ-RhoGEF blocks semaphorin 4D-induced growth cone collapse in primary hippocampal neurons. Our study indicates that the interaction of mammalian plexin-B family members with the multidomain proteins PDZ-RhoGEF and LARG represents an essential molecular link between plexin-B and localized, Rho-mediated downstream signaling events which underly various plexin-mediated cellular phenomena including axonal growth cone collapse. [Copyright &y& Elsevier]

Summary The mammalian pupillary light reflex (PLR) involves a bilateral brain circuit whereby afferent light signals in the optic nerve ultimately drive iris-sphincter-muscle contraction via excitatory cholinergic parasympathetic innervation [ 1, 2 ]. Additionally, the PLR in nocturnal and crepuscular sub-primate mammals has a “local” component in the isolated sphincter muscle [ 3–5 ], as in amphibians, fish, and bird [ 6–10 ]. In mouse, this local PLR requires the pigment melanopsin [ 5 ], originally found in intrinsically photosensitive retinal ganglion cells (ipRGCs) [ 11–19 ]. However, melanopsin’s presence and effector pathway locally in the iris remain uncertain. The sphincter muscle itself may express melanopsin [ 5 ], or its cholinergic parasympathetic innervation may be modulated by suggested intraocular axonal collaterals of ipRGCs traveling to the eye’s ciliary body or even to the iris [ 20–22 ]. Here, we show that the muscarinic receptor antagonist, atropine, eliminated the effect of acetylcholine (ACh), but not of light, on isolated mouse sphincter muscle. Conversely, selective genetic deletion of melanopsin in smooth muscle mostly removed the light-induced, but not the ACh-triggered, increase in isolated sphincter muscle’s tension and largely suppressed the local PLR in vivo. Thus, sphincter muscle cells are bona fide, albeit unconventional, photoreceptors. We found melanopsin expression in a small subset of mouse iris sphincter muscle cells, with the light-induced contractile signal apparently spreading through gap junctions into neighboring muscle cells. Light and ACh share a common signaling pathway in sphincter muscle. In summary, our experiments have provided details of a photosignaling process in the eye occurring entirely outside the retina. [ABSTRACT FROM AUTHOR]